How to access child components value in parent component in React

Currently I am using reat creat app to build my appication in my application had three componentes those are com1, com2, com3 I want to update userId state value in com1 based on com3 will recive props here com2 is child component of com1.

Here is my sample code

import comp2 from './comp2.js';
class comp1 extends React.Component {
    constructor(props) {
        super(props);

          this.state = {
          userId:""

         }
        };

    click() {
        this.setSate({userId:"123"});
    }

    render() {
          <div>Hello Child onClick={this.click}</>
          <comp2 data={this.state.userId}
    }
}

import comp3 from './comp3.js';
class comp2 extends React.Component {
    constructor(props) {
        super(props);
        };

        componentWillReceiveProps(nextProps) {
        if (nextProps.data !== this.props.data) {
         this.setState({userID:this.state.userId});
       }
 }
}


    click() {
         this.setState({userID:"456"})
    }

    render() {
          <div>Hello Child onClick={this.click}</>
          <comp3 data={this.state.userId}
    }
}

class comp3 extends React.Component {
    constructor(props) {
        super(props);
        };

    componentWillReceiveProps(nextProps) {
        if (nextProps.data !== this.props.data) {
         this.setState({userID:this.state.userId});
       }
 }

    render() {
          <div>Hello Child onClick={this.click}</>
          <comp3 data={this.state.userId}
    }
}